Well, I’ve always asked myself why can’t we use some kind of train or catapult to help the rockets to save fuel or to go further. Can anyone explain me why?
In: Engineering
There are actual ideas along those lines, but they are still theoretical because they would need to be extremely huge beyond anything we can easily build today.
The important thing is that it is not so much about getting into space (which is only a 100 km up) but getting into orbit which means going several dozen times the speed of sound on earth.
Rockets are difficult because you need to carry fuel to carry more fuel around, so that your typical rocket that goes into space is mostly fuel and very little actual payload.
This had let many to think of how we can do this easier, better and cheaper.
The most famous idea for an alternate orbital insertion system is the space elevator, basically climbing a rope up into space high enough that you reach the point where orbital velocity which you need to stay up is the same speed that you are already going thanks to the rotation of the planet.
Everyone agrees that such a space elevator would be wonderful and cheap and easy and generally much better than rockets with just the minor problem that we don’t have any materials strong enough to build one.
Other famous ideas include shooting up your spaceship in a giant gun. This is an idea that actually predates modern rocketry and another thing that would work in theory.
One problem is that chemical explosion based guns accelerate their projectile really really hard, so that would not work for anything fragile like humans. Magnet based rail guns could work with a much lower acceleration though.
The bigger problem is that any space gun would need to be enormous. It is another thing that would work in theory but that we don’t have the right tech for yet to actually build it. The last guy to actually spend serious money on building anything like that was Saddam Hussein and he was more concerned with reaching some place more down to earth rather than the stars. (Things didn’t work out well for him.)
Another thing that might be come close to a catapult would be a space bola or rotating space tether. It is basically a cut down version of a space elevator that rotates in orbit and has its ends reach down into the atmosphere where a fast flying plane could attack a payload to be catapulted up into higher orbit by the spinning death strand. It is close technology wise to what we might actually be able to build with current tech, but would still be a major undertaking.
In any case, anything that shoots or catapults stuff into space could save some rocket fuel but you would always need some rockets to make an actual orbit out of it.
The point is that people have thought along the lines you suggested, come up with ways that would work, but ended up not being able to built the things they came up with because we don’t have the materials or the money for that yet.
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